Other bacterial diseasesStaphylococcal zoonoses

Staphylococcal species are common commensals of the skin and mucous membranes of humans and animals but only in very recent years has zoonotic infections been recognised. They can also be associated with infection and disease, especially coagulase positive organisms. Staphylococcus aureus is relatively frequently carried by humans in the nasal passages and is a cause of infections in people including bacteraemias in hospitalised patients. More recently some strains of Staphylococcus aureus have acquired a resistance gene (mecA) which renders them resistant to meticillin (meticillin-resistant Staphylococcus aureus, MRSA). MRSA isolates are of major importance in healthcare situations as well as increasingly in the community. Animals can also be carriers of Staphylococcus aureus although less frequently than humans and MRSA can be carried or infect several different host species. For companion animals such as dogs and cats, the most frequently isolated MRSA strains are similar to the common local human healthcare strains; thus for the UK, EMRSA-15 and -16. This suggests a reverse zoonosis with spill over from the human population into their companion animals. In horses the situation is different, with some horses carrying or infected with human epidemic strains but others infected with strains less frequently seen in people. For food-producing animals the picture is different again with a particular strain, ST398, which appears to circulate endemically in animal populations, such as pigs, and can spill over into the human population where it can cause carriage as well as infection and disease. The transmission appears to be by direct contact with animals rather than through the food-chain.Where risk factors for infection with MRSA have been studied in animals they appear similar to some of the risks for human infection. Therefore, for control of MRSA in animals measures such as improved hygiene and good antibacterial stewardship are important.